This invention relates to improved rapping apparatus for plate type electrostatic precipitators. More particularly the novel invention relates to a rapping apparatus wherein the collector and discharge plates are rapped from the sides of the plates by a multiplicity of hanging, pivotal mounted hammers which are dragged past the plates and caused by interaction with the plates to be raised and then permitted to swing down in an arc to impact the side of an adjacent plate.
Precipitators to which this invention pertains are commercial plural plate precipitators used in factories and similar environment to collect and remove dust and other debris from exhaust gases, e.g., from power plants and industrial processes, to prevent discharge of such pollutants into the atmosphere. The exhausting gases pass between and parallel to a plurality of plates, alternate ones (discharge plates) of which are highly charged and the others (collector plates) being normally grounded. In a well-known manner, dust, debris and other pollutants are collected on the plates and the essentially cleaned gases pass on to the atmosphere, e.g., up a stack. In operation the pollutants build up on the plates and cause a decrease in efficiency. In accord with prior art teaching the plates are periodically rapped or struck with hammers to remove the collected material which drops into hoppers below the precipitator. The rapping mechanism in prior art devices are either edge rappers or side rappers.
Several examples of edge rappers are found in U.S. Pat. Nos. 2,668,600 to H. A. Wintermute; 3,570,217 to W. Steuernagel; and 3,844,742 to H. H. Petersen. A rapping mechanism which incorporates hammers acting on anvils connected to plates is shown in U.S. Pat. No. 4,519,817 to R. E. Gibbons and a beater type with swinging whips on a reciprocating bar used on a filter is shown in U.S. Pat. No. 2,196,839 to L. E. Seng.
Edge rappers are not proven to be particularly effective in generating the requisite vibratory forces in the plate for effecting dislodging of the collected material. There are some prior art side rappers which create hammer blows at the same time to all of the collector plates or all of the discharge plates during one reciprocation of the hammer carriers. While such side rapping constructions provide an effective force against the plates to dislodge the collected material, because 50% of the plate surfaces within the precipitator module are cleaned at one time, the result is a visible emission from the stack each time the plates are rapped.
The problems attending side rapping have existed for many years and prior efforts to reduce the number of plates cleaned at one time have not been successful.